Pulsed electromagnetic energy method for forming a film

ABSTRACT

A method of forming a film by a plasma CVD process in which a high density plasma is generated in the presence of a magnetic field wherein the electric power for generating the plasma has a pulsed waveform. The electric power typically is supplied by microwave, and the pulsed wave may be a complex wave having a two-step peak, or may be a complex wave obtained by complexing a pulsed wave with a stationary continuous wave.

This application is a Divisional of application Ser. No. 09/262,853filed Mar. 5, 1999 now U.S. Pat. No. 6,110,542; which itself is aDivision of Ser. No. 08/740,140, filed Oct. 22, 1996 now abandoned ;which is a Division of Ser. No. 08/463,058, filed Jun. 5, 1995, now U.S.Pat. No. 5,626,922; which is a Division of Ser. No. 08/426,483, filedApr. 20, 1995 (now abandoned); which is a Continuation of Ser. No.08/120,222, filed Sep. 14, 1993 (now abandoned); which is a Continuationof Ser. No. 07/763,595, filed Sep. 23, 1991 (now abandoned).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for forming a film.

2. Description of the Prior Art

Films have been heretofore deposited by various processes such as CVD(chemical vapor deposition), sputtering, MBE (molecular beam epitaxy),and the like. In plasma enhanced CVD (referred to simply hereinafter asplasma CVD), the use of high frequency excitation, microwave excitation,hybrid resonance and the like has been developed. Particularly in theplasma CVD process which utilizes a resonance with a magnetic field(referred to as “plasma CVD in magnetic field”, hereinafter), thedevelopment thereof has actively taken place and, because of its highfilm deposition efficiency which results from the use of a high densityplasma, its diversification in application has been expected. In thepractical film deposition in the presence of a magnetic field, however,a difficulty has been encountered to deposit uniform films on anirregular surface without being influenced by such surface irregularity.This difficulty has hindered practical progress of the microwave CVD inmagnetic field in the industries. The fact that a plasma CVD in magneticfield consumes an enormous amount of energy at its operation also is abar to its gaining popularity in the industrial field. A diamond-likecarbon (DLC) film can be uniformly deposited on a substrate as large as10 cm or more in diameter by the use of microwave plasma CVD in magneticfield. In the deposition of such DLC films by this process, the diamondnuclei formed in the vapor phase are trapped on the substrate upon theircontact with the substrate. Thus, the DLC film grows spread in a taperedform from each nucleus, and results in a film having poor adhesion withthe substrate. Furthermore, since the diamond crystals grow in a taperedform from a diamond nucleus center trapped on the substrate, acompression stress accumulates around the grain boundaries within theDLC film. The poor adhesion of the film with the substrate and thecompression stress within the film have constituted a hindrance to thepractical use of DLC films.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a process of depositinguniform films.

Another object of the present invention is to provide a process ofdepositing films with small power consumption.

Still another object of the present invention is to provide a process ofdepositing films which have excellent adhesion with substrates.

The foregoing objects and other objects have been achieved by depositingfilms by a plasma CVD process which takes advantage of the interactionbetween a magnetic field and an electric field, e.g. a high frequencyelectric field, induced by supplying an electric energy intermittently,or of that between a magnetic field and an electric field, e.g. a highfrequency electric field, induced by supplying thereto an electricenergy intermittently and a stationary electromagnetic energycontinuously which are superposed upon each other. The magnetic fieldmay be generated by supplying an electric energy intermittently.Alternatively, the magnetic field may be obtained by supplying either aDC current or a pulsed current to a Helmholtz coil. Furthermore, riseand decay of the pulsed current for generating the magnetic fieldintermittently and those of the electric power for generating theelectric field intermittently may be synchronized with each other. In atypical embodiment, a microwave electric energy is supplied to generatethe high frequency electric field.

In FIGS. 3(A), 3(B), and 3(C) are given examples of time versus power(effective value of power). FIG. 3(A) shows a shape having two differentpeak values. Such a power is particularly effective in increasingproduction of substances over a certain threshold value whilesuppressing the production of substances having an energy of productionlower than the threshold value. FIG. 3(B) shows time versus power(effective value of power) of a wave obtained by superposing a highfrequency electric wave supplied intermittently upon a low powerelectromagnetic stationary wave supplied continuously, wherein theinitial waves have the same frequency. FIG. 3(C) also shows time versuspower (effective value of power)of a wave obtained by superposing a highfrequency electric wave supplied intermittently upon a low powerelectromagnetic stationary wave supplied continuously, however, thefrequency of the initial waves are differed. The plasma CVD of thepresent invention is referred also to as a pulsed plasma CVD hereinaftersince the power has a pulse shape as shown in FIGS. 3(A) to 3(C). Theuse of waves obtained by the superposition enables rapid deposition ofthe films, and is useful when a stable plasma cannot be obtained only byan intermittently supplied wave due to the structural allowance of theapparatus or to the conditions restricting the film deposition process.Thus, from the characteristic of a pulsed plasma CVD which enables auniform formation of nuclei for film growth on the surface ofsubstrates, the process enables deposition of a highly homogeneous filmon an article having an irregular surface on one hand; on the otherhand, from the fact that a high electric power can be concentrated at apulse peak as compared with a stationary continuous power, the filmdeposition can be carried out at an increased efficiency.

To obtain a film of uniform thickness extended over a large area on asubstrate, the film deposition is conducted in an apparatus the innerpressure of which is elevated to a range of from 0.03 to 30 Torr,preferably, from 0.3 to 3 Torr, using a high density plasma takingadvantage of hybridized resonance. Since the pressure is maintainedhigh, the mean free path of the reactive gas is shortened to a range offrom 0.05 mm to several millimeters, particularly to 1 mm or less. Thisfacilitates dispersion of the reactive gas to various directions, whichis advantageous for depositing films on the sides of the articles havingirregular surfaces. Thus, the rate of film growth is accelerated.

The article to be coated with a film is placed either in a hybridizedresonance environment or in an activated environment remote from thehybridized resonance environment, to thereby coat the surface thereofwith the reaction product. To achieve efficient coating, the article islocated in the region at which a maximum electric field intensity of themicrowave power can be obtained, or in the vicinity thereof.Furthermore, to generate and maintain a high density plasma at apressure as high as in the range of from 0.03 to 30 Torr, an ECR(electron cyclotron resonance) should be generated in a columnar spaceunder a low vacuum of 1×10⁻⁴ to 1×10⁻⁵ Torr and a gas, a liquid, or asolid is then introduced into the columnar space to produce a plasma,which is then maintained under a high pressure in the range of from 0.03to 30 Torr, preferably from 0.3 to 30 Torr, so as to obtain a spacehaving a highly concentrated product gas, said concentration per volumebeing about 10² to 10⁴ times as large as the gas concentration normallyused in a conventional ECR CVD process. By thus realizing the particularenvironment, the film deposition of a material which undergoesdecomposition or reaction only at such a high pressure becomes possible.The particular films which can be obtained include carbon films, diamondfilms, i-carbon (carbon films containing diamonds or microcrystalgrains), DLC (diamond-like carbon films), and insulating ceramics, andmetallic films, in particular films of metal having high melting point.

In summary, the process according to the present invention utilizesplasma glow discharge and comprises a known microwave plasma CVS processto which a magnetic field is added to utilize the interaction of themagnetic field with the high frequency (micro wave) electric field.However, the ECR conditions are omitted from the process. The processaccording to the present invention conducts the film deposition in ahybridized resonance space using a high density plasma having a highenergy, under a high pressure in the range of from 0.03 to 30 Torr. Inthe process according to the present invention, the plasma excitation iscarried out with a pulsed wave or a combination of a pulsed wave and astationary continuous wave, as set forth above, under a high energystate in the hybridized resonance space to thereby generate activespecies at an increased amount and also to effect homogeneous nucleiformation on the surface of the substrate. This enables the formation ofa thin film material at an excellent reproducibility.

The power is supplied in pulses, as mentioned earlier, at an averagepower of from 1.5 to 30 KW with a peak pulse about three times theaverage power. The primary pulse should be supplied at a period of from1 to 30 ms, preferably from 5 to 8 ms. Since the intensity of themagnetic field can be varied as desired, it is another characteristic ofthe process according to the present invention that the resonancecondition can be set for not only the electrons but also for a specifiedion.

In the deposition of a DLC film, for example, a pulsed wave havingrelationship between time and power (effective value of power) as shownin FIG. 4 can be applied. Preferably, the bonding within the DLC film isin sp³ hybridization. The ratio of the dissociation energy for Sp³hybridization to that for sp² hybridization is 6:5. In FIG. 4, it can beseen that the first peak 30 is 6/5 times as high as the second peak 31.In this case, the energy for the first peak 30 is preferably smallerthan the dissociation energy of sp³ hybridization but maintained higherthan the dissociation energy of sp² hybridization, so as not to breakthe Sp³ hybridization bonding but to promote breakage of sp²hybridization bonding. More specifically, for example, the energy of thefirst peak is set in the range of from 5 to 50 KW, and that of thesecond peak is set in the range of from 4.1 to 46 KW. Furthermore, in apulsed high frequency plasma CVD, the nucleus formation is activatedwhile the growth of the formed nuclei is suppressed. Such a phenomenaresults in a uniform formation of crystal nuclei over the substrate,which is followed by a growth into a DLC film composed of columnarcrystals 29, said crystals being substantially one direction orientedtoward the upper direction, such as shown in FIG. 5. Thus, a DLC filmhaving a uniform crystal structure and dominant in sp³ hybridization canbe deposited at a high reproducibility, free from problems frequentlyencountered in conventional processes, such as the stress due to taperedfilm growth and the peeling off of the deposited film induced therefrom.The pulsed wave power may be acicular pulse power, as well as the powersshown in FIGS. 6(A) and 6(B).

In another embodiment according to the present invention, a light (suchas an ultraviolet (UV) light) may be simultaneously irradiated to theactivated species to maintain the activated state for a longer duration.That is, the process comprises irradiating a light (e.g., a UV light)simultaneously with the generation of a high density plasma by theinteraction of the pulsed microwave and the magnetic field, so thatatoms excited to a high energy state can survive even at locations 10 to50 cm distant from the area at which the maximum electric fieldintensity of the microwave power is obtained, i.e., the area at which ahigh density plasma is generated, since the high energy state issufficiently maintained even on the surface of the article. This processenables deposition of a thin film over a further larger area. In theembodiment according to the present invention, a cylindrical column wasestablished in such a space, and the article on which the film is to bedeposited was provided inside the column to effect film deposition.

The generation of the microwave (at an average power in the range offrom 1.5 to 30 KW) may be synchronized with the generation of themagnetic field using an electric power the pulse form of which is shownin FIG. 6(A). Alternatively, a multistep rectangular pulsed electricpower as shown in FIG. 6(B) or that as shown in FIG. 6(C) may be used inplace of the pulsed electric power illustrated in FIG. 6(A). A multisteprectangular pulsed wave may be applied, for example, in the depositionof a DLC film. Since the microwave and the magnetic field in thisinstance can be supplied with a peak power of about 5.0 to 50 KW if sucha pulsed wave is used, the result is about 30 to 40% increasedefficiency as compared with the case a plasma CVD apparatus is operatedin a magnetic field with an input of an ordinary continuous wave at apower of from 1.5 to 30 KW. This enables reduction of power consumptionof the plasma CVD apparatus operated in the presence of a magneticfield. The pulse duration of the pulsed wave should be in the range offrom 1 to 10 ms, more preferably, from 3 to 6 ms.

It is also clarified that a film composed of more densified crystalgrains can be uniformly deposited on the article irrespective of thesurface irregularities of the article by applying a pulsed wave to aplasma CVD process in a magnetic field. This is also an advantage of theprocess according to the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of an apparatus for microwave CVD in magneticfield according to the present invention;

FIG. 2(A) shows a magnetic field obtained as a result of a computersimulation;

FIG. 2(B) shows an electric field obtained as a result of a computersimulation;

FIGS. 3(A), 3(B), and 3(C) each show a pulsed waveform according to thepresent invention;

FIG. 4 shows a pulsed waveform according to the present invention;

FIG. 5 is a schematically shown cross sectional view of a DLC filmaccording to the present invention; and

FIGS. 6(A) to 6(C) each show a pulsed waveform according to the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS EXAMPLE 1

Referring first to FIG. 1, a microwave plasma CVD apparatus according tothe present invention, to which a magnetic field is applicable is shown.The apparatus comprises a plasma generating space 1, a supplementaryspace 2, Helmholtz coils 5 and 5′ for generating the magnetic field, apower source 25 to supply energy to the Helmholtz coils, a generator 4for generating pulsed microwaves (also for generating waves obtained bysuperimposing a pulsed wave upon a stationary continuous wave), a turbomolecular pump 8 which constitutes an evacuation system, a rotary pump14, a pressure control valve 11, pressure valves 12 and 13, a substrateholder 10′, an article 10 on which a film is deposited, a microwaveentrance window 15, a gas system 6 and 7, a water cooling system 18 and18′, a halogen lamp 20 powered by power source 23, a reflector 21, lens22 for focusing photo energy beam 24, and a heating space 3.

The article 10 to which a film is deposited is first set on thesubstrate holder 10′, and provided in a plasma generating space 1through the gate valve 16. The substrate holder 10′ is made of quartzlest it should disturb the microwave and the magnetic field. The wholeapparatus is evacuated to a vacuum of 1×10⁻⁶ Torr or higher using theturbo molecular pump 8 and a rotary pump 14. A gas which does notparticipate in the reaction (i.e., a gas which does not produce a solidupon decomposition reaction) such as hydrogen is introduced into theplasma generating space 1 through the gas system 6 at a flow rate of 30SCCM to adjust the pressure thereof to 1×10⁻⁴ Torr. Then, microwave of2.45 GHz is applied externally at a pulse period of 8 ms. The magneticfield is applied at about 2 KGauss using the Helmholtz coils 5 and 5′ tothereby generate a high density plasma in the plasma generating space 1.The gas is flown downward from the upper side of FIG. 1, however, it maybe flown upward from the lower portion of FIG. 1, or may be flown fromthe right to the left, or vice versa.

The gas which does not participate in the reaction or electrons having ahigh energy discharged from the high density plasma reach and clean thesurface of the article 10 on the substrate holder 10′. Then, whilecontinuously introducing the gas which does not participate in thereaction, a reacting material (which forms a solid upon decompositionand reaction) in the form of a gas, liquid, or solid, such as ahydrocarbon gas [e.g., acetylene (C₂H₂), ethylene (C₂H₄), and methane(CH₄)], a liquid carbon compound [e.g., ethanol (C₂H₅OH) and methanol(CH₃OH)], and a solid hydrocarbon [e.g., adamantane (C₁₀H₁₆) andnaphthalene (C₁₀H₈)] is introduced at a flow rate of 20 SCCM. Thereacting material is converted into a plasma by virtue of the energiessupplied thereto. The pressure inside the vessel is adjusted to therange of from 0.03 to 30 Torr, preferably in the range of from 0.1 to 3Torr, specifically 0.5 Torr, for example, while maintaining the plasmaalready generated inside the vessel. The product gas can be concentratedper unit volume by thus elevating the pressure of the vessel, and itresults in increasing the rate of film growth. A gas can reach anywhereon an irregular surface of an article by elevation of the pressureinside the vessel.

Thus, the thin film material is deposited in a process which comprisesonce generating a plasma under a low pressure, increasing theconcentration of the active species of the reacting gas whilemaintaining the plasma state, forming active species excited to a highenergy state, and depositing the active species on the article 10provided on the substrate holder 10′.

The magnetic field as shown in FIG. 1 is generated by a Helmholtz coilsystem using two ring-shaped coils 5 and 4′. A quarter of the electricfield and that of the magnetic field are shown in FIGS. 2(A) and 2(B).Referring to FIG. 2(A), the abscissa (X-axis) represents the horizontaldirection (the direction in which the reactive gas is discharged) of thespace 38, and the ordinate (R-axis) represents the direction along thediameter of the Helmholtz coil. The curves drawn in FIG. 2(A) representthe equipotential plane of the magnetic field. The numerals placed onthe curves indicate the intensity of the magnetic field obtained whenthe magnetic intensity of the Helmholtz coil 5 is about 2000 Gauss. Themagnetic field intensity over a large film-deposition area of thesubstrate in a region 100 in which the interaction between the electricfield and the magnetic field occurs can be controlled to a nearlyconstant valve (875 Gauss+185 Gauss) by adjusting the strength of themagnet 5, that is by adjusting current flowing through the Helmholtzcoil 5. FIG. 2(A) shows the equipotential planes in a magnetic field; inparticular, curve 26 is the equipotential plane in the magnetic fieldfor 875 Gauss, which corresponds to the ECR condition.

The region 100 in which the resonance condition is satisfied correspondsto the area having a maximum electric field intensity, as shown in FIG.2(B). In FIG. 2(B), the abscissa corresponds to the flow direction ofthe reactive gas as in FIG. 2(A), and the ordinate represents theintensity of the electric field (electric field strength).

It can be seen that the electric field region 100′ also yields a maximumintensity as well as the region 100. However, with reference to themagnetic field (FIG. 2(A)), it can be seen that equipotential planes inthe magnetic field are densely distributed in this region 100′. It canbe understood therefrom that a film deposited on the substrate in thisregion 100′ may have great variation in thickness along the diameterdirection (the direction along the ordinate in FIG. 2(A)), and that afavorable film is only obtainable in the region satisfying the ECRcondition, i.e., along 26′. In conclusion, no uniform and homogeneousfilm can be expected in the region 100′. Film formation on an articlemay be carried out in the region 100′ in the case where a film having adoughnut shape is formed.

A region in which the magnetic field maintains a constant value over alarge area and in which the electric field strength attains a maximumalso exists at a symmetrical position of the region 100 with respect tothe origin. It is certainly effective to carry out film deposition atsuch a region so long as there is no necessity of heating the substrate.It is difficult to obtain, however, a means to heat the substratewithout disturbance of the electric field generated by the microwave.

Upon considering the ease of mounting and demounting of the substrate aswell as the heating thereof, and the achievement of a uniform andhomogeneous film in view of the applicability of the process to theindustrial mass production, the region 100 as shown in FIG. 2(A)outstands as a position superior to other two regions.

As a consequence of the considerations set forth above, it was madepossible in this embodiment of the present invention to form a uniformand homogeneous film up to a 100-mm radius, more favorably, up to a50-mm radius if a circular substrate 10 is placed in the region 100. Toobtain a film having the same uniform thickness as that of the filmmentioned above but with a further larger area, e.g., a film having anarea 4 times as large as the film above, the frequency may be reduced to1.225 GHz from the present 2.45 GHZ to thereby double the diameter (thedirection along the R axis of FIG. 2(A)) of the deposition space.

A specific embodiment of a process using the complex pulse as shown inFIG. 3(A) can be exemplified by the deposition of a DLC film. It isknown that the favorable bonding in a DLC film is in the form of sp³hybridization, and the point persists on how to reduce the sp²hybridization which is formed simultaneously with the sp³ hybridizationduring the film deposition process. Since the ratio of the dissociationenergy for sp³ hybridization to that for sp² hybridization isapproximately 6:5, the number of sp³ hybridization can be certainlyincreased by setting the energy of the first peak in the range of from 5to 50 KW, and that of the second peak to about 5/6 of the first peak,i.e., in the range of from 4.1 to 46 KW. The cross section of the thinfilm was examined with a scanning electron microscope to observe diamondcrystals. As a result, it was confirmed that diamond crystals grew intogranules. Particularly, the size of the diamond crystals was from 5 to10 times as large as that of the diamond crystals deposited by applyinga conventional stationary (continuous) microwave. Furthermore, it wascustomary in the conventional diamond films that they deposit initiallyas crystals of small diameter and gradually grow into crystals of largerdiameter, and that they thereby suffer poor adhesion with thesubstrates. In the diamond crystals deposited by the pulsed wave processaccording to the present invention, however, the diamond crystals werelarge even at the interface with the depositing surface. Thus, a filmcan be formed on the substrate with the superior adhesion therebetweenby the process according to the present invention. The electron beamdiffraction image of the film revealed spots ascribed to single crystaldiamonds, and it can be seen therefrom that a diamond structure clearlydevelop in the film by applying a power at an average output of 1.5 KWor higher.

Processes which utilize the complex waves obtained from a pulsed waveand a stationary continuous wave as shown in FIGS. 3(B) and 3(C) can beapplied widely. In the case where waves of the same wavelength arecombined as is shown in FIG. 3(B), such as the combination of amicrowave with another microwave or that of a high frequency wave andanother high frequency wave, a uniform film can be deposited at a smallenergy consumption. If waves of differed wavelengths are combined asshown in FIG. 3(C), a film having excellent uniformity and adhesion canbe obtained, as exemplified by the case in which a pulsed microwave wasadded to a stationary continuous high frequency wave. Variouscombinations of the waves, for example, a complex of a pulsed DC with astationary continuous microwave, can be designed depending on theintended purpose. According to an embodiment according to the presentinvention, a polycrystalline film of silicon carbide can be deposited onthe substrate by using a gas of carbosilicide (methylsilane). It is alsopossible to deposit a boron nitride film by the process according to thepresent invention, by simultaneously flowing a boride (e.g., diborane)and a nitride (e.g., nitrogen) to effect the reaction therebetween.Furthermore, the process may be utilized for depositing thin films ofoxide superconductors such as Bi(bismuth)-based oxide superconductors,YBCO-type superconductors, Tl(thallium)-based oxide superconductors, andV(vanadium)-based (non-copper type) oxide superconductors. Similarly,thin films of aluminum nitride, aluminum oxide, zirconia, and boronphosphide can be deposited. Multilayered films thereof with diamond canbe produced as well. It is also an embodiment of the present inventionto deposit on an article, films of a metal having a high melting point,such as tungsten, titanium, and molybdenum or films of metal silicidesuch as tungsten silicide, titanium silicide, and molybdenum silicide;the metal film may be deposited by subjecting a halide or a hydride ofthe metal itself to a decomposition reaction on the article, and themetal silicide film may be deposited by reacting the halide or thehydride of the metal with silane.

EXAMPLE 2

A DLC film was deposited in the same manner as in Example 1, except forusing a microwave complex pulsed waveform power as shown in FIG. 4 inplace of the complex pulsed waveform power shown in FIG. 3(A). A pulsed2.45 GHz microwave power having a two-step peak composed of a first peak30 of 50 KW and a second peak 31 of 46 KW, with a pulse period of 8 mswas externally applied.

The electron beam diffraction image of the film was completely free fromhalo patterns ascribed to amorphous substances, and it revealed the filmto be composed of diamonds having high crystallinity. The cross sectionof the thin film was examined with a scanning electron microscope toobserve diamond crystals. As a result, it was confirmed that diamondcrystals grew into columnar crystals. Particularly, the size of thediamond crystals was from 5 to 10 times as large as that of the diamondcrystals deposited by applying a conventional stationary (continuous)microwave. Furthermore, it was customary in the conventional diamondfilms that they deposit initially as crystals of small diameter andgradually grow into crystals of larger diameter, and that they therebyhave poor adhesion with the substrates. In the diamond crystalsdeposited by the pulsed wave process according to the present invention,however, the diamond crystals were large even at the interface with thedepositing surface. Thus, a film can be formed on the substrate with thesuperior adhesion therebetween by the process according to the presentinvention. The electron beam diffraction image of the film revealedspots ascribed to single crystal diamonds, and it can be seen therefromthat a diamond structure clearly develop in the film by applying a powerat an average output of 1.5 KW or higher.

The conventional diamond film deposition process using a stationary wavecould only provide a 10 μ thick diamond film which easily undergoespeeling by simply rubbing the surface with bare hands. However, thepulsed wave process according to the present invention provides diamondfilms of the same thickness as the conventional ones but which arecompletely resistant against peeling even when they are rubbed with asand paper. That is, the pulsed wave process according to the presentinvention is capable of depositing thin films of diamond havingexcellent adhesion with the substrate.

EXAMPLE 3

A DLC film was deposited by applying a microwave electric power having apulsed waveform as shown in FIG. 6(A) synchronously with the electricpower applied to generate a magnetic field having a pulsed waveform asshown in FIG. 6(A). A pulsed 2.45 GHZ microwave having a peak value of 5KW was externally applied at a pulse period of 8 ms. The magnetic fieldwas similarly applied in pulses having a peak value of about 2 KGaussand at a pulse period of 8 ms, by operating the Helmholtz coils 5 and5′. The pulsed microwave and the magnetic field were completelysynchronized to thereby provide a high density plasma in the plasmagenerating space 1.

In the embodiment, a thin film diamond was synthesized using a hydrogendiluted methanol as the starting material, applying a microwave power atan average output of 1.5 KW (peak value: 3.4 KW) and a pulse period of 8ms. The cross section of the thin film was examined with a scanningelectron microscope to observe diamond crystals. As a result, it wasconfirmed that diamond crystals grew into granular crystals.Particularly, the size of the diamond crystals was from 5 to 10 times aslarge as that of the diamond crystals deposited by applying aconventional stationary (continuous) microwave. Furthermore, it wascustomary in the conventional diamond films that they deposit initiallyas crystals of small diameter and gradually grow into crystals of largerdiameter, and that they thereby suffer poor adhesion with thesubstrates. In the diamond crystals deposited by the pulsed wave processaccording to the present invention, however, the diamond crystals werelarge even at the interface with the depositing surface. Thus, a filmcan be formed on the substrate with the superior adhesion therebetweenby the process according to the present invention. The electron beamdiffraction image of the film revealed spots ascribed to single crystaldiamonds, and it can be seen therefrom that a diamond structure clearlydevelop in the film by applying a power at an average output of 1.5 KWor higher.

The experimentally developed process according to the present inventionenables deposition of partially crystallized thin films under a widerrange of film deposition conditions. Furthermore, the pulsed waveprocess according to the present invention enables deposition of uniformfilms on articles having irregularities on the depositing surface, at areduced energy consumption as compared with. the conventional processusing a stationary continuous waves.

While the invention has been described in detail and with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof.

What is claimed is:
 1. A method for forming a film comprising the stepsof: introducing a reactive gas into a reaction chamber; applying apulsed electromagnetic wave to said reactive gas to convert saidreactive gas into a plasma; applying a continuous electromagnetic waveto said reactive gas so that said continuous electromagnetic wave issuperposed on said pulsed electromagnetic wave; and forming the film ona surface of an object in said reaction chamber, wherein a power valueof said pulsed electromagnetic wave is higher than a power value of saidcontinuous electromagnetic wave.
 2. A method according to claim 1wherein said film comprises a material selected from the groupconsisting of silicon carbide, aluminum nitride, aluminum oxide,zirconia and boron phosphide.
 3. A method for forming a film comprisingthe steps of: introducing a reactive gas into a reaction chamber;applying a pulsed microwave to said reactive gas to convert saidreactive gas into a plasma; applying a continuous electromagnetic waveto said reactive gas so that said continuous electromagnetic wave issuperposed on said pulsed microwave; and forming the film on a surfaceof an object in the reaction chamber using the plasma, wherein a powervalue of said pulsed microwave is higher than a power value of saidcontinuous electromagnetic wave.
 4. A method according to claim 3wherein said film comprises a material selected from the groupconsisting of silicon carbide, aluminum nitride, aluminum oxide,zirconia and boron phosphide.
 5. A method according to claim 3 wheresaid film comprises a material selected from the group consisting oftungsten, titanium and molybdenum, and a silicide thereof.
 6. A methodfor forming a film comprising the steps of: introducing a reactive gasinto a reaction chamber; applying a pulsed electromagnetic wave to saidreactive gas to convert said reactive gas into a plasma; applying acontinuous electromagnetic wave to said reactive gas so that saidcontinuous electromagnetic wave is superposed on said pulsedelectromagnetic wave; and forming the film on a surface of an object insaid reaction chamber, wherein a power value of said pulsedelectromagnetic wave is higher than a power value of said continuouselectromagnetic wave, and wherein a frequency of said pulsedelectromagnetic wave is the same as a frequency of said continuouselectromagnetic wave.
 7. A method according to claim 6 wherein said filmcomprises a material selected from the group consisting of siliconcarbide, aluminum nitride, aluminum oxide, zirconia and boron phosphide.8. A method according to claim 6 wherein said film comprises a materialselected from the group consisting of tungsten, titanium and molybdenum,and a silicide thereof.
 9. A method according to claim 6 furthercomprising a step of applying a magnetic field for performing anelectron cyclotron resonance in said reaction chamber.
 10. A methodaccording to claim 6 wherein said film comprises carbon having sp³hybridization bondings.
 11. A method for forming a film comprising thesteps of: introducing a reactive gas into a reaction chamber; applying apulsed electromagnetic wave to said reactive gas to convert saidreactive gas into a plasma; applying a continuous electromagnetic waveto said reactive gas so that said continuous electromagnetic wave issuperposed on said pulsed electromagnetic wave; and forming the film ona surface of an object in said reaction chamber, wherein a power valueof said pulsed electromagnetic wave is higher than a power value of saidcontinuous electromagnetic wave, and wherein a frequency of said pulsedelectromagnetic wave is different from a frequency of said continuouselectromagnetic wave.
 12. A method according to claim 11 wherein saidfilm comprises a material selected from the group consisting of siliconcarbide, aluminum nitride, aluminum oxide, zirconia and boron phosphide.13. A method according to claim 11 wherein said film comprises amaterial selected from the group consisting of tungsten, titanium andmolybdenum, and a silicide thereof.
 14. A method according to claim 11further comprising a step of applying a magnetic field for performing anelectron cyclotron resonance in said reaction chamber.
 15. A methodaccording to claim 11 wherein said film comprises carbon having sp³hybridization bondings.
 16. A method for forming a film comprisingdiamond-like carbon, said method comprising the steps of: introducing areactive gas into a reaction chamber; applying a pulsed electromagneticwave to said reactive gas to convert said reactive gas into a plasma;applying a continuous electromagnetic wave to said reactive gas so thatsaid continuous electromagnetic wave is superposed on said pulsedelectromagnetic wave; and forming the film comprising diamond-likecarbon on a surface of an object in said reaction chamber, wherein apower value of said pulsed electromagnetic wave is higher than a powervalue of said continuous electromagnetic wave, and wherein a frequencyof said pulsed electromagnetic wave is the same as a frequency of saidcontinuous electromagnetic wave.
 17. A method according to claim 16further comprising a step of applying a magnetic field for performing anelectron cyclotron resonance in said reaction chamber.
 18. A method forforming a film comprising diamond-like carbon, said method comprisingthe steps of: introducing a reactive gas into a reaction chamber;applying a pulsed electromagnetic wave to said reactive gas to convertsaid reactive gas into a plasma; applying a continuous electromagneticwave to said reactive gas so that said continuous electromagnetic waveis superposed on said pulsed electromagnetic wave; and forming the filmcomprising diamond-like carbon on a surface of an object in saidreaction chamber, wherein a power value of said pulsed electromagneticwave is higher than a power value of said continuous electromagneticwave, and wherein a frequency of said pulsed electromagnetic wave isdifferent from a frequency of said continuous electromagnetic wave. 19.A method according to claim 18 further comprising a step of applying amagnetic field for performing an electron cyclotron resonance in saidreaction chamber.